In this technical field, some research and development on next-generation communication systems have been intensively accelerated. In currently anticipated communication systems, a single-carrier scheme may be promising for use in uplinks from the viewpoint of wider coverage while avoiding increase in PAPR (peak-to-Average Power Ratio). Also in these communication systems, both uplink and downlink radio resources may be assigned in channels shared between multiple users depending on respective communication conditions of the users. Operations for determining such assignment may be referred to as scheduling. For appropriate scheduling in uplinks, each user apparatus transmits a pilot channel to a base station, and the base station evaluates channel condition of the uplinks based on reception quality. Also for scheduling in downlinks, the base station transmits a pilot channel to the user apparatus, and the user apparatus informs the base station of information (CQI: Channel Quality Indicator) indicative of channel conditions based on reception quality of the pilot channel. The base station evaluates the channel conditions of the downlinks based on the CQIs reported from the user apparatuses and accordingly schedules the downlinks.
Uplink control channels may include two types of control information, control information (requisite control information or first control information) that must be transmitted concomitantly to uplink data channels, and control information (second control information) that may be transmitted independent of the presence of the uplink data channels. The first control information may include information necessary to demodulate the data channels such as data channel modulation schemes and channel coding rates. The second control information may include downlink channel CQI information, downlink data channel acknowledgement information (ACK/NACK), resource assignment requests and/or others. Accordingly, the user apparatus may transmit only the first control information, only the second control information or both the first and second control information in the uplink control channels.
In the case where a resource block (radio resource) is assigned for transmission of the uplink data channel, the first control information (and the second control information as needed) may be transmitted in that resource block. On the other hand, if no uplink data channel is transmitted, it is assumed that the second control information is transmitted in a dedicated resource (dedicated band). Some examples of such band utilization are outlined below.
FIG. 1 illustrates exemplary uplink band utilization. In the illustrated example, two types of resource units of greater and smaller data sizes are provided. The larger resource unit may have a bandwidth FRB1 of 1.25 MHz and a duration TRB of 0.5 ms. The smaller resource unit may have a bandwidth FRB2 of 375 kHz and the duration TRB of 0.5 ms. The duration may be referred to as a unit transmission period, a transmission time interval (TTI) or a subframe. The duration may correspond to duration of a single radio packet. Six resources are arranged in the direction of frequency axis, and the smaller resources are arranged in the rightmost and leftmost locations. Various arrangement patterns of the resources can be designed as long as both the transmitter side and the receiver side have knowledge of them. In the illustrated example, uplinks are scheduled to transmit control channels (first control channels) being concomitant to uplink data channels together with the second control channels as needed in partial intervals in the larger resources (second, third, fourth and fifth resource blocks). Also in the smaller resources (first and sixth resources), transmission timings of user apparatuses are adjusted to transmit control channels (second control channels) for the case of no transmission of the uplink data channels. In addition, two smaller resources are used to transmit the first control channel for a certain user apparatus. In the illustrated example, the second control channel for user apparatus A is transmitted in the sixth resource in the second subframe and the first resource in the third subframe. Similarly, the second control channel for user apparatus B is transmitted in the sixth resource in the third subframe and the first resource in the fourth subframe. In this manner, the second control channels are transmitted such that they are hopped with respect to the frequency axis and the time axis. As a result, time and frequency diversities can be obtained, resulting in higher reliability of successful demodulation of the second control channels at the base station.
FIG. 2 illustrates another exemplary uplink band utilization. Similar to the example illustrated in FIG. 1, two types of resource units of greater and smaller data sizes are provided. In this example, the subframe duration TRB is subdivided into two subintervals for the smaller resources (first and sixth resources). In the illustrated example, the second control channel for user apparatus A is transmitted in the first subinterval (the first half of the subframe interval) of the first resource in the first subframe and in the second subinterval (the second half of the subframe interval) of the sixth resource in the first subframe. The second control channel for user apparatus B is transmitted in the first subinterval of the sixth resource in the first subframe and in the second subinterval of the first resource in the first subframe. The same transmission may be also performed in the third and fifth subframes. In this manner, the second control channels are transmitted so that they are hopped with respect to the frequency axis and the time axis. As a result, time and frequency diversities can be obtained, resulting in higher reliability of successful demodulation of the second control channels at the base station. In addition, the transmission of the control channel for user apparatus A may be completed within the single subframe, and the transmission of the control channel for user apparatus B may be also completed within the single subframe. Thus, this example may be preferred from the viewpoint of shorter transmission latency of the uplink control channels. This technique is described in non-patent document 1“3GPP, R1-061675”, for example.